Food products such as restaurant and grocery store carry out are transported in various food containers. One type of container is a paperboard container. Some paperboard containers allow for storage, transportation, and preparation of food. For example, paperboard containers may be provided with plastic covers for storage and transportation of food products. Standard plastic covers—such as oriented polystyrene covers—for such containers are dependent upon the dimensions of the container for their effectiveness. These OPS dome closures may be provided with compound skirts having undercuts for interference locking with the container's flange. In such a container-and-closure combination, a single cover may be adapted for use with a single size of container, and these closures are very sensitive to the top outside dimensions of the container to be covered. Additionally, such closures are sensitive to the top outside shape of the container to be covered. Further, such container-and-closure combinations provide an inadequate seal against the flow of liquids out of the container. Other container covers currently utilized include plastic heat seal films and aluminum foil wraps. However, these container cover types present several challenges including, the need for special equipment, a lack of puncture resistance, a lack of tolerance to dimensional variation, and dubious sealing qualities against the flow of liquids.
An example of a typical prior art paper board container is shown in FIG. 1. The container or tray 10 of FIG. 1 has a bottom 12 from which side walls 14 extend upwardly, terminating at a flange 16. The flange 16 of the tray 10 extends outwardly from the tops of the side walls 14 in a direction approximately parallel to the bottom 12 of the tray 10.
The tray 10 is a paperboard tray, formed from a pressed sheet of paperboard and provided with creases 18 where the paperboard has been compressed into a rectangular shape forming the basin 20 of the tray.
Trays such as the tray 10 may be formed with sharp or rounded corners, and the corners may be formed by gathering pleats, or folding a number of scores. The side walls 14 of the tray 10 are at an angle to the bottom 12 of the tray. This type of construction provides a certain amount of variation of the top outside dimensions (i.e., the width W and the length L of the tray at the outermost reaches of the flange 16). The variation in the top outside dimensions is largely a function of changes in the angles of the side walls 14. For example, for paperboard scored and formed into a food container, in some cases the resultant variation in the top outside dimensions can be as much as +/− 3/32 of an inch between two different trays. This dimensional variation makes the fit and lock of a formed lid difficult, because such a lid is generally designed for use with trays falling within a much smaller dimensional variation. Further, formed containers using pleats to form the corners are subject to reduced rigidity, because the pleats become pivot points allowing increased flexibility of the food container. The reduced rigidity also presents formed closure fit and lock difficulties.
It is desirable for a container closure or lid to have greater tolerance for use with trays of different dimensions. Further, it is desirable for a container closure or lid to proved a more complete seal against the flow of liquids from the container. Finally, it is preferable for such a container-and-lid combination to be convenient and easy to use. The present invention is directed to an improved closure or lid and to containers employing improved closures or lids.